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Materials 2011, 4(6), 1168-1181; doi:10.3390/ma4061168

Delocalization of Electrons in Strong Insulators at High Dynamic Pressures

Department of Physics, Harvard University, Cambridge, MA 02138, USA
Received: 28 May 2011 / Accepted: 13 June 2011 / Published: 21 June 2011
(This article belongs to the Special Issue Hard Materials: Advances in Synthesis and Understanding)
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Systematics of material responses to shock flows at high dynamic pressures are discussed. Dissipation in shock flows drives structural and electronic transitions or crossovers, such as used to synthesize metallic liquid hydrogen and most probably Al2O3 metallic glass. The term “metal” here means electrical conduction in a degenerate system, which occurs by band overlap in degenerate condensed matter, rather than by thermal ionization in a non-degenerate plasma. Since H2 and probably disordered Al2O3 become poor metals with minimum metallic conductivity (MMC) virtually all insulators with intermediate strengths do so as well under dynamic compression. That is, the magnitude of strength determines the split between thermal energy and disorder, which determines material response. These crossovers occur via a transition from insulators with electrons localized in chemical bonds to poor metals with electron energy bands. For example, radial extents of outermost electrons of Al and O atoms are 7 a0 and 4 a0, respectively, much greater than 1.7 a0 needed for onset of hybridization at 300 GPa. All such insulators are Mott insulators, provided the term “correlated electrons” includes chemical bonds.
Keywords: dynamic pressure; metallic liquid H; oxide metallic glasses dynamic pressure; metallic liquid H; oxide metallic glasses
This is an open access article distributed under the Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Nellis, W.J. Delocalization of Electrons in Strong Insulators at High Dynamic Pressures. Materials 2011, 4, 1168-1181.

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